Lower limb nerve injuries

Question 1

Prolapsed intervertebral disc

Describe the myotome and dermatome affected for each nerve root compressed

L4

L5

S1

Answer 1

• weakness in dorsiflexion, parasthesia in medial leg and ankle
• weakness in great oe extension, parasthesia in lateral leg and dorsum of foot
• weakness in plantarflexion, parasthesia in lateral foot border, sole of foot and heel)

Question 2

Piriformis syndrome

What is it?

What are the symptoms?

What causes it?

What are the treatments?

Answer 2

• Sciatic like symptoms that do not originate from compression of spinal nerve roots but due to compression of sciatic nerve by piriformis muscle
• dull ache in buttock, sciatica in thigh, leg and foot, pain when walking up stairs
• spasm of piriformis muscle - overuse (athelets)
• activity modification, NSAIDs, physiotherapy

Question 3

Sciatic nerve injury

If sciatic nerve complretely transected in buttock, what effects would this have on movement and sensation of lower limb?

Answer 3

• Hip extension normal: hamstring paralysed but glut max funcitoning (inferior gluteal nerve)
• Hip flexion normal: hip flexor muscles (femoral nerve)
• hip adduction normal: adductor muscles (obturator nerves)
• Hip abduction normal : glut max and min (superior gluteal nerve)
• Knee extension normal : knee extensors(femoral nerve)
• Knee flexion absent : knee flexors (sciatic nerve)
• dorsiflexion, plantar flexion, toes movement absent
• Cutaneous distribution ; common fibular (lat leg, dorsal foot, tibial (palmar foot, posterior lat leg)

Question 4

Meralgia paraesthetica

What is it?

What causes it?

What are the symptoms?

What is the positive sign?

How is the diagnosed made?

Answer 4

• compression of the lateral femoral cutaneous nerve as it pierces the inguinal ligament
• obesity, pregnancy, tight clothing
• brning sensation over anterolateral aspect of thigh, aggrevated by walking, relieved by lying down with hip flexed
• Tinel’s sign
• absence of motor sign, exclude pelvic and intra-abdominal causes of nerve irritation like tumor

Question 6

Saphenous nerve injury

What causes it?

Where is it prone to injury?

Answer 6

• saphenous vein cut down, orthopedic surgery to medial malleolus, saphenous vein harvest
• subcutaneous course in medial leg